Growth and ability of Senna alata in phytoremediation of soil contaminated with heavy metals

Abstract

The performance and impact of Senna alata on experimental heavy metal contaminated soil were investigated in this study. Soils in different pots were contaminated with different levels of lead, nickel, chromium and cadmium based on WHO limits for heavy metals. Seeds of S. alata were planted in the contaminated soils. The plant growth was studied for 60 days. Some soil parameters and heavy metal contents of the soil were evaluated at the beginning and at the end of the study. The leaf area, the plant height and the number of actively growing stems decreased with increase in the amount of each metal added to the soil. At 60 days, there was significant reduction (p<0.05) of the heavy metals due to the growth of S. alata compared to the soil without the plant. There was reduction in the total organic matter content and the pH of the soil, but the moisture content of the contaminated soils generally increased due to the growth of S. alata. There was a positive correlation (p = 0.918) between the percentage remediation and the bioaccumulation factor, suggesting that the remediation of the heavy metals by the plant mostly occurred through bioaccumulation. A positive correlation between the percentage reduction of the heavy metals and the reduction of pH of the soil noticed suggests that growth of S. alata leads to decrease in soil pH and will enhance the remediation of soil contaminated with the heavy metals. The findings of this study show that apart from the medicinal values of S. alata, it can be useful in remediation of heavy metal polluted soils which occurs mostly through phytoextraction.